Cell signalling by ion channels

Question 1

what is another name for ligand-gated ion channels?

Answer 1

ionotropic receptors

Question 2

what is a ligand-gated ion channel?

Answer 2

A multi-subunit protein that crosses through the plasma membrane
- the channel may be closed or open

Question 3

how do molecules move through ligand-gated ion channels?

Answer 3

when open ions move into, or out of, the cell depending on their electrochemical gradient

Question 4

what determines the ion that can move through a ligand-gated ion channel?

Answer 4

the type of ion(s) moving through the channel is determined by the channel’s structure

Question 5

what are some stimuli that can open ligand-gated ion channels?

Answer 5

• changes in voltage across the membrane
• deformation of the membrane
• ligands at the cell surface

-some channels are always open
- a further class of ion channel are opened in response to internal signals

Question 6

what are GIRK’s and what is their function?

Answer 6

G-protein gated inwardly-rectifying potassium channels
- they allow K+ to move out of a cell

Question 7

what signals do ligand-gated ion channels provide?

Answer 7

rapid and normally short lasting signals to cells

particularly well suited to signalling in the nervous system

Question 8

what is the structure of ligand-gated ion channels?

Answer 8

-channels are composed of multiple subunits
- 4 to 5, the number depending on the channel type
- each protein subunit makes 4 passes across the membrane

Question 9

what is the most important ligand-gated receptor?

Answer 9

receptor at the neuromuscular junction

Question 10

what is the receptor at the neuromuscular junction?

Answer 10

nicotinic acetylcholine receptor

Question 11

what is the structure of the nicotinic acetylcholine receptor?

Answer 11

made up of 5 subunits

found in different regions and these have different subunit structures

Question 12

what is the function of the nicotinic acetylcholine receptor?

Answer 12

influx of Na+ causes the muscle to depolarize

Question 13

where are nicotinic acetylcholine receptors found?

Answer 13

present in the brain and elsewhere

Question 14

how does the acetylcholine receptor function?

Answer 14

as part of a complex with other proteins

Question 15

what is rapsyn?

Answer 15

anchors the nicotinic acetylcholine receptor to the membrane

Question 16

what is the function of rapsyn?

Answer 16

concentrates the nAChR at the correct location opposite the synapse

Question 17

how does being in a complex help the nicotinic acetylcholine receptor?

Answer 17

complex involved in correctly maintaining the positioning of the receptor for most effective functioning

Question 18

what does loss of dystrophin result in?

Answer 18

Duchenne Muscular Dystrophy, an X-linked muscle wasting disorder

Question 19

what are the two types of glutamate receptors present at some synapses?

Answer 19

AMPA receptors
NMDA receptors

Question 20

what is an AMPA receptor?

Answer 20

ion channels that allow Na+ into the post-synaptic target cell

Question 21

what is an NMDA receptor?

Answer 21

ion channels that allow Ca2+ into the post-synaptic target cell

Question 22

what happens when Ca2+ enters the post-synaptic target cell?

Answer 22

an increase in Ca2+ can stimulate multiple cellular events including protein kinases

Question 23

what happens when kinases are activated in the post-synaptic target cell?

Answer 23

activation of kinases (including CaMKII) can mediate many intracellular actions

Question 24

what is the function of the protein kinase CaMKII?

Answer 24

CaMKII plays an important role in long term potentiation (a mechanism involved in memory formation)